The invention is directed to a process for the production of pyridines substituted in the 2-position by an aromatic or heteroaromatic group. These substituted pyridines are important intermediate products for the production of medicines, plant protective agents and synthetic resins. For example 2,2'-dipyridyl is used to produce the known herbicide 1,1'-ethylene-2,2'-dipyridilium dibromide.
It is known to form 2-phenyl pyridine in addition to 4-phenyl pyridine by the action of benzene diazonium chloride on pyridine (Berichte Vol. 26, (1893) pages 2003 to 2004). 2-Phenyl pyridine is also produced by the reaction of phenyl lithium with pyridine (Organic Synthesis Vol. 18 (1938) pages 70 to 71) or by the addition of butadiene to vinyl pyridine and dehydrogenation of the 2-cyclohexene pyridine formed (J. Amer. Chem. Soc. Vol. 75 (1953) pages 4738 to 4740). Also, it is known to produce 2,2'-dipyridyl by reduction of pyridin-1-oxide with sodium in liquid ammonia (Chem. Abst. Vol. 49 (1955) 15895f) or by heating 2-bromopyridine with copper powder (Angew. Chem. Vol. 46 (1933) pages 21 to 22 or by heating pyridine with Raney-nickel (Organic Synthesis Vol. 46 (1966) pages 5 to 10).
These processes are little suited for use in producing the substituted pyridines on an industrial scale. They are expensive and cumbersome to handle. The yields are moderate. Besides in several cases, the starting materials are only difficulty accessible.